You can turn the machine on to test it by all means - check the HDD activity. After about 3 mins - if no sound of video is witnessed - then I assume the Amiga is potentially dead due to battery leakage.

I advise to remove the computer - called the Expality - to check for battery leakage asap.

On the rear of the SD, there will be 2 x  4mm hex key locks. Turn these to unlock and remove the rear cover. Unplug the power cable to the cooling fans.
Looking in the rear, you will see many cables attached to the computer, they are `Nearly` all different to each other. I will list them below - read before unplugging.
Remove all the cables (read first)
On the rear left, you will see a small latch, open this, that then will enable the `tray` that the computer sits on, to slide forwards (as long as its not damaged like mine was)
Now at the front of the machine, (I hope you have the key!) open the front plate, and pull the upright forwards, then lift the whole plate out. If it has foot pedals, be careful of disconnecting the cable to them.
There may be a cable for the keyboard plugged in to the front - remove this if there is.
Slide the computer forwards on the tray, and lift it out - beware - its about 35Kg.

On the left of the computer, there should be three low profile cooling fans, on a removable plate. Remove the plate. 3mm hex key required - and the hope for non-rusted in screws!
(I replaced all my screws with M4 x 16mm crosshead screws)
Careful - again, disconnect the power cable to the fans.

Right, inside you will see the expansion cards: 1 or 2 graphics cards and a network.
The network card is at the top.
If one graphics card - you should see two silver components at the back of the card - these are timing oscillators
If two graphics cards - there will be one oscillator on each card, and link with between the cards.
Another note... it may not have any at all - just two empty 8-pin sockets

Removing these cards will make it easier to get to the battery - but you`ll have to disconnect the connections to the card at the back - which is awkward if the `Expality` back panel is still on.
(to dismantle the Expality - see below) 
You `Dont` have to remove the cards at this point.
Get a torch and light up the main board under the cards, and you will see the blue battery. Its soldered in place, but with a fine and sharp pair of cutters and a VERY careful hand, the battery can be snipped off - its not needed and just causes more damage if left.

Right : Rear panel cables: (if same as mine - if a OLD machine - most cables may just got through a large hole.
most are different type of plug, different pins, different gender.
Same ones are :
Control Panel and Tracker Source. control panel cable is tie-wrapped to the monitor one - the Tracker Source is a single cable.
Joystick Right is the same as both tracker senors.
You should only have one tracker connection - T1. - this cable will go up to the loom for the headset
Joystick cables are thicker and go direct to each joystick.